Most often, a manufacturer of products packages a plurality of products, sometimes called a lot, into cases for storage and subsequent shipping to distributors. The quantity of products in the case is referred to as a case lot quantity. At some point during the distribution of the product, a manufacturer or a distributor may be required to break open a case for further distribution of the products in less than case lot quantities. Frequently, products in less than case lot quantities are assembled with other products pursuant to an order that includes more than one product.
A distributor or manufacturer who supplies less than case lot quantities must pick products from the cases, referred to as broken case order picking, before shipping an order that includes a selection of products. Filling an order for multiple products in less than case lot quantities requires going to a case for each product, picking and counting the number of units of the product from the case, and assembling the picked products to be shipped into a single container. These tasks have, in the past been performed manually. People, though, are relatively slow and prone to pick or pull wrong products and incorrect quantities from the cases and may even forget to pull a particular product. Automation of broken case picking is, consequently, preferred in order to minimize the number of incorrectly filled orders and the costs resulting from picking errors.
Automated ordering systems (AOS) are available to automate the picking process. In a typical AOS, a terminal operator receives an order and types it into the system on a keyboard as a part of a terminal coupled to a host computer. The host computer handles accounting and inventory control functions for the distribution operation. The host computer provides the order to a workstation for handling or editing. When the order is ready to be executed, a central control computer as a part of the work station directs in real time the filling of the order.
An AOS is comprised, in essence, of a plurality of individual product dispensers stocked with different types products that are arrayed along the length of a gathering conveyor belt. In some systems there are literally hundreds or thousands of different products and product dispensers. The gathering conveyor belt is constantly moving. The central control computer segments or defines virtually, in memory, one or more gathering conveyor belts into order zones, separated by buffer zones, in which are collected products for filling an order. As a virtual order zone for a particular order moves past a product dispenser stocking a selected product, the central control computer directs a programmable logic controller associated with that product dispenser to cause the product dispenser to dispense the ordered quantity of the product.
Product dispensers in an AOS singulate the products for counting--a product dispenser dispenses only one product at a time--and verifies that the products have been dispensed. Typically, associated with each product dispenser is a photoelectric cell or some other means for detecting a product to verify that a product is actually dispensed. In order to ensure that a product dispenser actually dispenses an ordered quantity of product into an order zone as it passes the dispenser, the product dispenser must be capable of rapidly ejecting products onto the gathering belt. To achieve rapid rates of dispensing, a force must generally be applied to the product. Given that product dispensers must singulate and rapidly eject products, elaborate means for dispensing and means for controlling the dispenser are required, especially as throughput of an AOS is increased.
Product dispensers must also address the problem of replenishing the stock of products in each dispenser. The stock in some product dispensers is replenished manually; others have elaborate automated means for replenishing. Whatever method is chosen, a replenishing system must be provided, usually complicating the effort to achieve an optimum design of the product dispenser and sometimes demanding compromise.
Finally, the cost of automation limits the use of an AOS such has been described to high volume products. In most broken case distribution operations, about twenty percent of the different types of products account for eighty percent of the total volume of products picked and shipped. There may be, for example, products handled by the distribution operation that are picked only once a month. The return on investment for incorporating products picked only once a day, much less once a month, rarely justifies automation. The high cost of an AOS, therefore, deters automation for most of the broken case operations.
Prior art product dispensers for an AOS are directed to high volume picking, high volume being required to achieve a sufficiently high return on investment to justify automation. The prior art tends, therefore, to teach against automating lower volume products. Consequently, approaches to low volume picking do not utilize AOS that have been described. Instead, the low volume approaches analogize to manual picking. One such approach, called a "flying dutchman", utilizes a sled mounted on a track beneath magazines holding products. The sled speeds back and forth along the track picking with a mechanism on the sled products from the magazines and placing them on the sled, much like a person manually picking products. It has the advantage of requiring a minimal number of dispensing mechanisms, but at the expense of, among other disadvantages, requiring a very sophisticated and expensive control mechanism for moving the sled and picking mechanism. Another approach is the use of robotic carts roaming the warehouse. It too suffers from complicated controls.